1. Field of the Invention
The present invention relates to an image forming apparatus capable of outputting an image having relatively heightened glossiness at a part of the image to be output.
2. Description of the Related Art
Recently, there has been a demand to adjust the glossiness of a print product to be output as well as to improve image quality thereof. For example, an expression method called a gloss mark method to express a figure and a character by heightening glossiness at a desired area with a gloss difference against other areas has been known.
Such a figure drawn with a gloss difference (hereinafter, called a gloss mark) cannot be copied by a copying machine which performs copying as a reading density of a printed image. Because of the difficulty of being copied (i.e., high original assurance), a gloss mark is sometimes called a security mark. Further, since an area having different gloss can be formed purposely on an output image of one sheet with a gloss mark, a desired position can be distinguished. Therefore, the expression boundaries of a print product can be expanded.
A configuration to use clear toner without a pigment at an area of which gloss is desired to be heightened in order to form such a gloss mark on a sheet has been discussed in Japanese Patent Application Laid-Open No. 4-338984. By mounting clear toner on the area having gloss to be heightened (i.e., a gloss mark part), gloss can be heightened. Further, by changing the clear toner quantity used at the gloss mark part, the gloss mark is formed to be distinguished or formed not to be distinguished according to a user's wishes.
However, with the configuration of Japanese Patent Application Laid-Open No. 4-338984 to utilize clear toner for outputting a gloss mark, it is necessary to prepare clear toner in addition to colored toner. Further, a storage container, a supply mechanism and a development device are necessary for clear toner. Accordingly, such an image forming body has an increased size in addition to an increased manufacturing cost.